<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>用户登录案例</title>
   
</head>
<body>
    <script src="https://cdn.staticfile.org/vue/2.2.2/vue.min.js"></script>
    <div id="app">
        <span v-if="isUser">
            <label for="uesrname">用户账号</label>
            <!-- 加key不能复用 -->
            <input type="text" id="username" placeholder="用户账号" key="username">
        </span>
        <span v-else>
            <label for="email">用户邮箱</label>
            <input type="text" id="email" placeholder="用户邮箱" key="email">
        </span>
        <button @click="isUser = !isUser">切换类型</button>
    </div>
    <script>
        const app = new Vue({
            el: "#app",
            data: {
                isUser: true
            },
            methods: {
               
            }

        })
    </script>
</body>
</html>